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Motasem M. Al-latayfeh, Ashley Mullins, Qun Zeng, Kwang-Soo Kim, John O. Trent, Henry J. Kaplan, Robert A. Mitchell, Tongalp H. Tezel; Neutralization of Macrophage Migration Inhibitory Factor (MIF) can Prevent Proliferative Vitreoretinopathy (PVR) by Inhibiting Epithelio-Mesenchymal Transformation (EMT) of Retinal Pigment Epithelium (RPE). Invest. Ophthalmol. Vis. Sci. 2011;52(14):6592.
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To determine whether MIF inhibition can prevent the formation PVR by blocking EMT of RPE.
Primary human RPE cells from two young donors (20 and 26 years old) were plated on tissue-culture plastic and maintained in DMEM H16 supplemented with 10%FBS and a MIF inhibitor (4-IPP, 25-50 µM) for 3 weeks. Control cells were exposed only to the solvent (DMSO/Corn oil). Morphology and qPCR for microphthalmia transcription factor (MITF), plasminogen activator inhibitor type-1 (PAI-1), vimentin and N-cadherin was used to asses the presence of EMT. The effect of MIF inhibition on EMT was further tested in vivo using an animal model of PVR. 6 adult C57BL/6 mice were anesthetized with an IP pentobarbital sodium (70 mg/kg) and a linear incision was made in the cornea. The lens was removed and a tear was created in the peripheral retina using a 32G needle. Corneal incision was then sutured with 10-0 nylon. Experimental group received 500 µg/in 5 µl of a MIF inhibitor (ACT-003) in the posterior subtenon space on Days 0 and 5 whereas control animals received the solvent. Animals were sacrificed on Day 10 and light microscopy was used to asses the presence and extend of PVR. MIF -/- animals (n=3) were also used as control.
Cultured human RPE cells treated with MIF-inhibitor were significantly fewer in number but maintained their typical cuboidal epithelial morphology, in contrast to control RPE that acquired a fibroblast-like morphology. Consistent with the cell morphology, MIF neutralization resulted in the reduction of mRNA levels of mesenchymal markers (vimentin, 8.5x; PAI-1, 19.7x and N-cadherin, 43,2x) and an increase in mRNA levels of the epithelial gene product, MITF (1.6x). In control eyes, surgically-induced retinal detachment was complicated with the formation of epi- and subretinal fibrotic membranes, as well as multilayering of the RPE cells. RPE cells remained as a monolayer in the experimental group that received MIF-inhibitor and in MIF -/- animals. Neutralization of MIF significantly inhibited the formation of peri-retinal membranes.
MIF is an important regulator of EMT in RPE. Neutralization of MIF is a potential therapeutic target for the prevention and treatment of ocular proliferative disorders such as PVR.
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